The best place to fit a radiator is beneath the window in a room as cold air falling by the window will be balanced by the warm air rising from the radiator. This idea directs heat in front of the curtains instead of behind them allowing more heat to be retained within the home instead of losing heat behind the curtains. Water fills between the double layer tubes and as it gets heated the hot air gathers within the tubes and rises through the centre of each tube and through vents at the top, heat also radiates outwards.